Much as I know it's fashionable to batter the AW courses, bear in mind that Lingfield also stages as many turf fixtures per Flat season as any other! Plus a handful of NH ones, too. The newest leaflets state 'Lingfield Park Racing Country Club' so the idea there is for the hotel/spa to attract people for golf 'n' racing weekdays/weekends/weeks, while perhaps their Good Ladeeze relax under hot stones or hotter masseurs.
You say 'if Lingfield weren't being paid to stage meetings' - you might as well say that about every course, since SIS lob them all at least £4,000 a race - but that isn't Lingfield or Southwell or Goodwood or Hereford or Bath or Ayr's doing. SIS wanted picture rights to show in all the betting shops, and the courses wanted paying to give them those rights, and that's the offer SIS made on behalf of all the bookies and punters who want to see their horses run, without the need to visit a course.
The course does attract plenty of non-racing income but, as I've said perhaps only 458 times before, racecourses keep separate income streams from racing, and non-racing, activity. The non-racing activity income does not go into racing's pot - it goes to fund the maintenance and/or expansion of those facilities (bars, kitchens, restaurants, the salaries of catering staff and the admin staff administering them). It doesn't go into buying a new irrigator for the turf or a replacement harrow for the AW!
Without picture rights, most small courses would fold their tents and become housing or light industrial sites. For example, Folkestone (Arena) is planning to sell off enough of its land to a developer to build on it some 800 houses, close down for at least a year, reshape the actual course, knock down and build a new grandstand and related facilities - it couldn't possibly do that relying on gate turnout alone. Gate takes, including hospitality bookings and high-priced restaurant packages, don't generate enough to pay staff, insurances, utilities (think of the water bills environmentally unfriendly turf courses incur), vehicles, buildings' maintenance, world without end. Picture rights are keeping a lot of courses going in these days of alternative amusements.
Your point about diversification would be met by a corporate answer that as racing alone (i.e. as a spectacle) can't generate additional business, it needs all these add-ons to attract slightly more sophisticated racegoers than, say, 20 years and more ago. And because, as I've said before, there's so much other competition to take the public away from racedays. Shopping, for example, has taken on a life as a social activity, rather than a boring chore to be got through as quickly as possible. People now hugely combine it with food and drink, and make an occasion out of it. So, it's right in that added on-course facilities do attract more people to come racing as it's now seen much more as a social event than just a place for old boys in battered trilbies; yet it's not right that the income stream thus generated goes back directly into racing. It helps racing in that it puts more bums on velour seats, but it doesn't mean that the profits from the Christmas parties, birthday bashes and weddings go to fund higher prize money for owners, or new rakes for the groundsmen. It will go, in a circular fashion, back to itself.